1. Field of Invention
Invention relates to a hydraulic driven turning device that can be installed to a construction machine, such as at the end of a boom of a power shovel whereupon a first body and another body, which is turning in relation to it, belong to the turning device and a hydraulic cylinder, which is attached from the mentioned bodies to one body, belong to the device in which cylinder the piston that is located in there can be moved axially back and forth with the help of a hydraulic pressure medium and a spiral part is attached to the piston that causes a rotation movement to its counter part that is equipped with a spiral whereupon the mentioned rotation movement can be transferred to be the turning movement of another body.
2. Description of the Prior Art
Hydraulic driven turning devices according to the above mentioned introduction are previously known in which devices ring piston, which can be moved back and forth with the help of a hydraulic pressure, is installed on top of a axis to be directed in axial direction in such a way that there is a spiral with large pitch between them whereupon a rotation movement is created between them when only another one of them can move in axial direction. Further there is a spiral with large pitch at the outer surface of the ring piston which spiral co-operates with the spiral of the barrel that is outside it. The movement of the mentioned barrel is locked in axial direction whereupon it rotates in relation to the piston if the piston is being moved. The another body of the turning device is attached non rotating to the mentioned barrel and another body is attached to the mentioned axis to be non rotating and the axial movement of the piston makes then the bodies to turn with each other.
This kind of known turning device is expensive to manufacture because spirals, which can be manufactured on four different surfaces in a relatively difficult way, belong to it. In these solutions ring piston is used as a piston whereupon its diameter has to be measured to be larger than a disc-like piston when its power-creating surface area! can be achieved only from the ring part. Also in these known solutions, parts that can be moved and are to be sealed are used a lot.